I was just experimenting with your code and successfully did my first “sandbox” payment. I believe that in SetExpressCheckout there is a small error fixed by:
return urllib.unquote(response_token)
in that very function (the tokens have a url escaped dash in them, mybe not when you wrote the function so the next functions double-quote it)

Anyway, it all works and I’m happy with it.

I was wondering if you could be convinced in showing your python logic for the retun dics from GetExpressCheckoutDetails and DoExpressCheckoutPayment. Do you just check for ACK: Success or do you check more fields.

Kindest,

- Bram